Insect flower-visitors of African oil palm Elaeis guineensis at different sites and distances from natural vegetation in Uganda

Abstract

This survey aimed at generating information to guide improvement of oil palm fruit-set in Uganda by testing the hypothesis that diversity and abundance of oil palm insect flower-visitors were influenced by sampling site, distance from natural vegetation and flower sex. Sampling was done on male and female oil palm flowers from (i) five oil palm experimental fields in different districts and (ii) oil palm plantations on Bugala Island on Lake Victoria. The plantations on Bugala Island were subdivided into near (0–15 m) and far (100–200 m) from natural vegetation. We recorded 162,677 insects in 23 morpho-species, dominated by weevils in the genera Elaeidobius and Metamasius (Family: Curculionidae); beetles (Families: Nitidulidae, Staphylinidae and Scarabidae); Diptera (Families: Muscidae, Drosophilidae and Platystomatidae); and honeybees (Apis mellifera), respectively. All morpho-species occurred on both flower sexes, except four Elaeidobius spp which occurred on only male flowers. All morpho-species recorded on both flower sexes were more abundant on male than female flowers, except Apis mellifera and one Elaeidobius sp whose mean counts were comparable between flower sexes. The insects were more abundant and divers on oil palm trees near a natural vegetation than on those positioned farther away; and on the Island than the mainland sites. This suggests a need for location specific interventions and manipulation of natural vegetation in designing strategies for boosting oil palm pollination in Uganda. Further research is necessary to understand ecology and biology of the identified oil palm flower visitors to boost oil palm pollination in Uganda.